I think Mike Shaw stated the matter for good using fromerly cited examples of darts and guns.
Strictly speaking accuracy and precision are sort of independent. If your mean (average) shot is on the target then you are accurate even if you never hit the target precisely. Your shots may be off the target by a large distance. You are accurate so long as the mean shot is on the target. If the dispersion of your shots is small then you are precise. Of course your shots do not have to converge on the target. So it may happen that you are extremely precise but not accurate like if your darts all converged on lower right corner within a radius of an inch. Using darts (or shooting) you may have examples of any compbination of accuracy and precision. "Shooting" examples are best because they clearly show what "closeness of mean to target" and dispersion (measured by standard deviation) mean. But concepts of accuracy and precision apply everywhere in life. Not surprisingly the distinction between the two is very clear in technology, navigation and gunnery even if terms are used interchangeably. I would add another remark. Precision is costly and you know it very well even from sundialing experience. Accuracy is related to your attitude and skills. Precision depends on apparatus and resources you have at hand. So if you are not accurate in general, then the best precision probably will not help you because you focus off the target or on the wrong target. As a rule we should be always accurate and as precise as we can afford it. Slawek At 10:44 PM 4/29/99 +0100, you wrote: >Fire 10 shots from a gun at a target. >If the 10 holes in the target are tightly grouped, but near >the outer, you are precise but not accurate >If they are loosely grouped evenly around the bull, you are >accurate, but not precise. >If you can get them tightly grouped around the bull, you >are precise and accurate > >In mathematical terms: >Accuracy is the closeness of the mean to the target figure >Precision is indicated by the standard deviation > >I think > >Off to the annual BSS conference tomorrow for an >entertaining weekend. >Hope to see some of you there. > >Mike Shaw > >[EMAIL PROTECTED] >53.37N 3.02W > > > Slawek Grzechnik 32 57.4'N 117 08.8'W http://home.san.rr.com/slawek
